a good musician never stops learning ... band practices will be a learning experience in themselves because you'll be interacting with the rest of the band, the drummer (and rhythm guitarist, presuming your group has two guitarists) especially. pay extra special attention to your drummer's kick drum foot - that's your mutual note.
also, tape your practices with a cassette deck or mini-disc recorder and listen for mistakes! then archive those tapes and in a year or so when you're doing good, you can always pull them out for a good laugh - "holy ****, were we terrible during that prac session! i didn't know my a-sharp from my b-flat!"
